Molecular oxygen reacts spontaneously in neutral solutions with certain metal-peptide complexes to oxidize the peptides. Copper and nickel catalyze this activation of O2, but the copper reaction is subject to photochemical inhibition. Trivalent copper and trivalent nickel are formed in O2 reactions and their role in catalyzing the oxygen uptake will be examined. The electrode potentials of Cu(III)-peptides and Ni(III)-peptides will be determined as a function of the nature of the coordination groups. The Cu(III) and Ni(III) peptide complexes will be generaged by electrolysis and studied in regard to (1) the stoichiometry of their decomposition in acidic and in basic solutions, (2) their role as catalysts in the autoxidation reactions, (3) their photochemical decomposition, and (4) their redox reactions with one-electron and two-electron reducing agents. The overall objectives are to determine the scope, extent, specificity, mechanisms, and biological significance of the metal catalyzed autoxidations and the nature and properties of Cu(III) and Ni(III) complexes. BIBLIOGRAPHIC REFERENCES: "Characterization of a Readily Accessible Copper(III)-Peptide Complex," D.W. Margerum, K.L. Chellappa, F.P. Bossu, and G.L. Burce, J.Am. Chem. Soc., 97, 6894 (1975). "The Stabilization of Trivalent Nickel in Deprotonated-Peptide Complexes," F.P. Bossu and D.W. Margerum, J.Am. Chem. Soc., scheduled for publication in June, 1976.